The present invention relates generally to coupling apparatus, and more particularly provides a uniquely configured shock-absorbing resilient coupling which is coaxially connectable between driving and driven shafts to transmit rotational power therebetween.
As exemplified in U.S. Pat. Nos. 1,701,470; 2,199,926; 2,712,742; 3,034,443; 3,466,869; and 3,859,821, a variety of coupling designs have heretofore been proposed for resiliently interconnecting driving and driven shafts to transmit rotational power therebetween. A common theme has been to provide a relatively flat resilient member, connect an end portion of one of the shafts to a central section of the resilient member, and connect an end portion of the other shaft to a peripheral portion of the resilient member. This connection utilizes torsional shear stress in the resilient member to provide for rotational flexure between the coupled shafts.
More specifically, when a torsional load is transmitted between the shafts (whether such load is a steady state torque or a transitory torsional shock), outer and inner portions of the resilient member are axially twisted relative to one another. While this relative twisting scheme is satisfactory in some shaft-coupling applications, in many high-torque situations the risk is present that a sudden torsional shock (or other unexpected torque load) can cause actual shearing of the resilient member, thereby creating a "spin-out" condition in the coupling a condition in which the resilient member is simply ripped apart, thereby eliminating the connection between the two shafts.
Various alternative coupling designs have been proposed to eliminate this shear-induced failure problem. One such design utilizes essentially circular coaxial inner and outer coupling members having overlapping radial tab portions thereon which define around the inner member an array of axially extending chambers. Resilient inserts are removable positioned in such chamber, between each pair of radial tabs, and are compressed by the tabs when the inner and outer coupling members are rotated relative to one another half of the inserts being compressed when the coupling members rotate in one direction relative to one another, the other inserts being compressed when the members are rotated in the other direction. This type of coupling is relatively expensive to manufacture and assemble. Moreover, since only half of the inserts are compressively stressed during relative rotation in a given sense between the two coupling members, this type of coupling configuration is notably inefficient as to its use of the internal resilient material. Further, couplings of this type typically can absorb only torsional forces, and cannot resiliently resist axially directed thrust loads.
It is accordingly an object of the present invention to provide a shock-absorbing resilient coupling which eliminates or substantially minimizes the above-mentioned and other problems and limitations typically associated with resilient torquetransmitting couplings of conventional construction and operation.
A representative torque transmission application in which torsional shock and vibration pose a variety of heretofore unsolved problems is in the drive train of large diesel-powered trucks in which a powerful, high compression diesel engine operates through a manual transmission to drive a differential system connected to the transmission by an elongated drive shaft having a universal joint at its differential driving end. This conventional drive train system typically incorporated in large trucks generates considerable torsional shock and vibration along its length due to the essentially rigid torsional interconnection between the diesel engine and the differential. The torsional shock and vibration not only significantly shorten the lives of various drive train components, but is also transmitted to the truck cab to an extent that can rapidly cause driver fatigue.
A conventional approach to reducing the amount of drive train shock and vibration transmitted to the driver has been to provide truck cabs with rather elaborate and expensive air suspension systems designed to isolate the driver from- such shock and vibration. This, of course, does not eliminate torsional drive train shock and vibration, and its life-shortening effects on drive train components. It merely forms a shock and vibration absorbing buffer between the driver and the drive train.
Various attempts have heretofore been made to incorporate a resilient link into the otherwise essentially rigid (from a torque transmission standpoint) drive train of a motor vehicle to torsionally "soften" the transmission-differential interconnection. Illustrative of this resilient link approach is U.S. Pat. No. 1,906,057 to Guy in which the normal yoke-type universal joint is replaced with a resilient universal joint formed from a metal sheathed rubber element press-fitted between overlapping driving and driven shaft end portions. As another example, a resilient coupling employing an annular rubber member captively retained between inner and outer cup-shaped members is secured to a universal joint yoke in the resilient universal joint structure illustrated and described in U.S. Pat. No. 2,949,021 to Charlesworth.
While these and similar conventional rubber-based coupling components indeed add resiliency to a motor vehicle drive train, they simply do not have the strength and longevity to function satisfactorily in a diesel truck application with its widely diverging torque and speed characteristics. It is accordingly a further object of the present invention to provide more durable shock-absorbing resilient coupling apparatus which may be incorporated into the drive train of a diesel truck to significantly reduce drive train shock and vibration transmitted to the driver, and to prolong the operating life of various other drive train components.